1. Field of the Invention
This invention relates to a video switch and related switching method, and in particular, it relates to an asynchronous video switch and related switching method.
2. Description of Related Art
In recent years, HDMI interface, which is a digital transmission interface more efficient and faster than the DVI interface, has been developed. More and more digital audio and video equipment (such as playback device, display device, etc.) are now adopting this interface. Also, a High-Bandwidth Digital Content Protection (HDCP) standard is developed in recent years to protect copyright of digital audio and video content and prevent illegal duplication or spreading of such content during transmission or playing. The HDCP standard includes an authentication protocol; using such a protocol, the HDCP transmitting device (such as a playback device) can confirm whether a particular HDCP receiving device (e.g. a display device) is authorized to receive content protected by HDCP. When access right is confirmed, the content protected by HDCP security protection can be transmitted from the HDCP transmitting device to the HDCP receiving device using a shared secret key which is established during the authentication process, to prevent illegal capture of HDCP protected content by an illegitimate device.
However, as shown in FIG. 1, when the display device switches to a different image, for lower end televisions, the time required from reading the Extended Display Identification Data (EDID) and confirming the HDCP authentication data (i.e. the first authentication, “auth-1”) to outputting the image is approximately 4 seconds. For higher end televisions, this time is approximately 1 to 2 seconds. Moreover, when switching images, the display screen is blank (i.e. no image is shown). These cause long delays and undesirable visual effect for the viewer.